Multi-line laser radar

ABSTRACT

A multi-line Lidar is provided. The multi-line Lidar includes: a multi-line ranging laser emission module comprising one or more lasers; a multi-line ranging laser reception module comprising one or more photodetectors and adapted to detect a laser echo generated when a measurement laser emitted by the laser emission module is incident to an obstacle and is diffusedly reflected; a ranging information resolution module in electrical signal connection with the multi-line ranging laser emission module and the multi-line ranging laser reception module, and designed to calculate the distance, in each direction, to the obstacle by means of calculating the time difference between the emission of the measurement laser and the receiving of the laser echo; and a control circuit and an optical system correspondingly configured for the multi-line ranging laser emission module and the multi-line ranging laser reception module.

This application is a National Phase Application of PCT InternationalPatent Application No. PCT/CN2018/087045, filed on May 16, 2018, whichclaims priority to Chinese Patent Application No. 201720656433.1, titled“WIRELESS COMMUNICATION APPARATUS AND LASER RADAR”, filed with theChinese Patent Office on Jun. 7, 2017, Chinese Patent Application No.201720713800.7 titled “LASER RADAR BASED ON MULTIPLE LASER DEVICES WITHNONUNIFORM DISTRIBUTION”, filed with the Chinese Patent Office on Jun.19, 2017, and Chinese Patent Application No. 201711312298.X titled“LASER RADAR SYSTEM”, filed with the Chinese Patent Office on Dec. 8,2017, all of which are incorporated herein by reference in theirentireties.

FIELD

The present disclosure relates to a multi-line Lidar.

BACKGROUND

Laser ranging technologies based on Time of flight have been widelyapplied to various fields.

For a single-line Lidar, only one beam of scanning laser is generatedalong an axial direction, and a two-dimensional scenario is sensed bychanging an angle of the one beam of the scanning laser in a horizontalplane. That is, the single-line Lidar may sense a scenario in a plane ora curved surface scanned by the one beam of scanning laser. In an actualapplication, in order to sense a three-dimensional scenario by thesingle-line Lidar, the single-line Lidar is required to be moved so thatvarious frames of two-dimensional images may be combined to generate athree-dimensional effect.

In order to obtain three-dimensional information of the scanned regionas much as possible, a multi-line Lidar which can cover a largervertical field of view is generally adopted. For the multi-line Lidar inthe current market, the angular separations of the laser beams areuniformly distributed in a certain angle range (that is, the verticalangular resolution has pre-determined values). For example, for the16-line, 32-line and 64-lineLidar Lidars of Velodyne, the verticalangular resolutions are 2 degrees, 1.33 degrees and 0.43 degreerespectively. For the 4-line and 8-line Lidars of Ibeo, the verticalangular resolution is 0.8 degree.

A vehicle-mounted Lidar is mainly configured to detect pedestrians andvehicles or the like on the ground. In this case, if the vertical fieldof view has been evenly assigned in an upper field of view and a lowerfield of view, a substantial amount of the beams pointing upward are notuseful.

In addition, if the distribution pattern of the current products isfollowed and the vertical angular separations are distributed uniformly,more lines are required to realize a higher vertical angular resolution,resulting in a higher cost, a larger volume and a lower reliability andstability. Due to the limitation of a data capacity of the Ethernet anda processing speed of the vehicle-mounted CPU, a Lidar with a highernumber of laser beams cannot satisfy the requirements of both a highlevel of vertical angular resolution and a high scanning frequency ofthe Lidar.

If the number of lines is decreased based on the cost, the angularseparation will become very large, and thus the target in a shortdistance range (for example 40m) may not be detected. For example, ifthe vertical field of view is 32° and the angular separation is 2° (thevertical resolution), 16 lines are required to cover the vertical fieldof view. As a result, the gap among laser beams at a distance of 40 mwill be about 1.4 meters. With such a large gap, it is easy for theLidar to miss a pedestrian.

According to a determination whether an emission optical path overlapswith a receiving optical path, the Lidar may be classified into acoaxial system and a non-coaxial system. For any Lidar, in order toensure that all the emitted laser pulses enter a receiving field of viewof the Lidar after passing through a blind area and a transition area ofthe Lidar, the emitted laser pulses should be parallel with an opticalaxis of a receiving telescope. Once directivity of the emitted beamchanges, the overlap factor correction curve of the Lidar cannot bedetermined, and a correct correction result cannot be provided for theoverlap region. The laser beam may deviate from the receiving field ofview when the directivity severely deviates, resulting in that the Lidarcannot detect the obstacle.

In the conventional Lidar system, due to offset of a reflector, anoperation ambient temperature of a semiconductor laser device, platformvibration, wavelength change and a service life of the semiconductorlaser device, it is difficult to ensure that the emitted beams maintaincoaxial or parallel to the optical axis of the receiving telescope inthe non-coaxial Lidar system. In addition, space is scanned throughrotation of one-dimensional galvanometer in the conventional Lidarsystem, and the requirement for scanning field of view of the Lidarcannot be satisfied. In addition, the rotation of the galvanometer iscontrolled through a mechanical structure, resulting in increasedmaintenance difficulty and limited measurement accuracy.

SUMMARY

An object of the present disclosure is to provide a multi-line Lidar,which can measure distances of obstacles in different directions,generate a three-dimensional point cloud, directly sense athree-dimensional scenario, and can detect a key region more accuratelyin a case of controlling a cost caused due to the number of laser beamsof the Lidar.

The technical problem can be solved by a multi-line Lidar according tothe present disclosure. The multi-line Lidar includes an emissionmodule, a receiving module, a ranging information determination moduleand a control circuit and an optical system for the emission module andthe receiving module. The emission module includes one or more laserdevices. The receiving module includes one or more photon detectors andis configured to detect an echo signal generated by the backscatteringof emitted laser beams by an obstacle. The ranging informationdetermination module is coupled with the emission module and thereceiving module via electrical signals, and is configured to determinedistances of obstacles in predetermined directions based on a time delaybetween a first time instant when the emission module emits themeasurement laser and a second time instant when the echo signal isreceived by the receiving module.

According to a preferred implementation of the multi-line Lidar of thepresent disclosure, the emission module is configured to emit multiplelaser beams with nonuniform vertical angular resolutions. That is, angledifferences between adjacent laser beams are not the same in a verticaldirection. The nonuniform vertical angular resolutions indicate that themultiple laser beams are distributed with different densities fordifferent heights. Compared with the laser beams with uniform spacingfor detecting ranges, more laser beams can be provided to key heightregions according to the solution of the present disclosure. In anembodiment, the numbers of the laser devices and the photon detectorscorrespond to the number of laser beams of the multi-line Lidar.

According to a preferred implementation of the multi-line Lidar of thepresent disclosure, the control circuit includes a time-to-digitalconverter. The ranging information determination module is configured todetermine the time delay between the time instant when the emissionmodule emits the laser beam and the time instant when the echo signal isreceived by the receiving module based on a time delay between a timeinstant when the emission module sends a first signal to thetime-to-digital converter and a time instant when the receiving modulesends a second signal to the time-to-digital converter in response todetecting return laser, to calculate the distance of the obstacles inthe direction.

In an alternative implementation, the time delay is obtained indirectlyby comparing current waveforms. The control circuit includes ananalog-to-digital converter configured to collect and digitize, in realtime, current waveforms of the emission module and the receiving module.The ranging information determination module is configured to comparethe current waveform of the emission module and the current waveform ofthe receiving module for determining the time delay between the timeinstant when the emission module emits the laser beam and the timeinstant when the echo signal is received by the receiving module, tocalculate the distance of the obstacles in the direction.

According to a preferred implementation of the multi-line Lidar of thepresent disclosure, the emission module is configured to transmitmultiple laser beams in a manner that an upper region and a lower regionhave a sparer vertical angular resolution along a vertical field of viewthan a middle region. In this case, the emitted laser beams aredistributed densely in a horizontal line and regions close to thehorizontal line, and is distributed sparsely in other directions.

The emitted laser beams are distributed with such nonuniform verticalangular resolutions, so that a high vertical angular resolution can berealized with the low number of laser beams, thereby saving a cost anddecreasing a volume of the device. In particularly, in consideration ofa fact that obstacles to be identified (such as pedestrians andvehicles) during traveling of a vehicle are generally focused at thehorizontal line and regions close to the ground, the distributiondensity of central laser beams (at the horizontal line and near thehorizontal line) is increased, and such nonuniform laser beamdistribution is more scientific and reasonable for the actual trafficenvironment. From another angle, the number of laser beams is decreasedin a non-key regions accordingly when the number of laser beams in thekey regions is increased, so that the total number of laser beams iscontrolled, thereby ensuring realization of a high scanning frequency,and generating a more accurate scanning result in a case of meetingrequirements of a high horizontal angular resolution and the highscanning frequency.

A technical solution regarding various angles at which the laser beamscans over time in the vertical direction is provided. For example, inan alternative implementation, the multiple laser beams emitted from theemission module include one beam of laser having an angle changing overtime in the vertical direction. In another alternative implementation,the multiple laser beams emitted by the laser emission module includemultiple beams of laser having angles changing over time in the verticaldirection.

According to a preferred implementation of the multi-line Lidar of thepresent disclosure, the multi-line Lidar further includes a scanningmodule configured to change an angle of the multiple laser beams overtime in the vertical direction. The laser beam having the angle changingover time in the vertical direction may be deflected to a correspondingangle in the vertical direction by, for example, one-dimensional ortwo-dimensional galvanometer. The galvanometer is configured to changethe angle of the laser beam over time in the vertical direction.

In an embodiment, a dichroic module is arranged in an emission opticalpath and a receiving optical path of the multi-line Lidar, and thedichroic module is disposed on a same axis with the emission module andthe scanning module. The dichroic module is configured to transmit alaser beam emitted from the emission module to the scanning module andreflect an echo signal from an obstacle of the scanning module to thereceiving module.

According to a preferred implementation of the multi-line Lidar of thepresent disclosure, the multi-line Lidar further includes: a rotatingstructure, a stationary structure, a rotation mechanism, a communicationsystem and an electrical energy transmission system. The emission moduleand the receiving module are attached to the rotating structure. Thestationary structure has an external communication interface and anexternal power supply interface. The electrical energy transmissionsystem supplies external electrical energy to the rotating structure viathe external power supply interface. The rotation mechanism isconfigured to drive the rotating structure to rotate with respect to thestationary structure, and includes a feedback device. The feedbackdevice is configured to detect a rotational angle of the rotationmechanism in a horizontal direction. The communication system and theelectrical energy transmission system are arranged between thestationary structure and the rotating structure. In this case, spatialangles when the laser beam encounters the obstacle can be determined,and thus a position and a shape of the obstacle can be determinedaccording to the spatial angles in combination with the distance of theobstacles calculated based on the time delay.

The stationary structure is configured to fix the multi-line Lidar withan external connection structure. The external communication interfaceprovided in the stationary structure is configured to receive anexternal instruction, and transmit point cloud information and so onscanned by the multi-line Lidar to the outside. The external powersupply interface is configured to receive electrical energy inputtedfrom the outside.

The rotating structure may rotate around a fixed axis in a verticaldirection. The axis may be installed on the stationary structure or therotating structure. With rotation of the rotating structure, theemission module and the receiving module perform measurements fordifferent angles in the horizontal direction.

According to a preferred implementation of the multi-line Lidar of thepresent disclosure, the stationary structure is provided with anemission coil and a first modulation circuit, and the rotating structureis provided with a receiving coil and a second modulation circuit.Electrical energy is transmitted from the emission coil to the receivingcoil by electromagnetic induction.

In an alternative implementation, the stationary structure is connectedto the rotating structure via a slip ring. The slip ring includes twoportions which are rotatable to each other and are connected to thestationary structure and the rotating structure respectively. Aconductive channel is formed the two portions of the slip ring. Theconductive channel is configured to transmit electrical energy betweenthe stationary structure and the rotating structure.

According to a preferred implementation of the multi-line Lidar of thepresent disclosure, the communication system between the stationarystructure and the rotating structure includes a signal channel formed bythe two portions of the slip ring.

In an alternative implementation, communication between the stationarystructure and the rotating structure is performed by photoelectricconversion. Here, the communication system between the stationarystructure and the rotating structure includes: a light emitting diodearranged on the stationary structure, a photodiode arranged on therotating structure, a light emitting diode arranged on the rotatingstructure and a photodiode arranged on the stationary structure. Thelight emitting diode arranged on the stationary structure is configuredto convert an electrical signal to be transmitted into an opticalsignal, and the optical signal is captured and converted into anelectrical signal by the photodiode arranged on the rotating structure.The light emitting diode arranged on the rotating structure isconfigured to convert an electric signal to be transmitted into anoptical signal, and the optical signal is captured and converted into anelectrical signal by the photodiode arranged on the rotating structure.

In addition, any conventional wireless sending and receiving device maybe considered. For example, in alternative implementations, thecommunication system between the stationary structure and the rotatingstructure may include a wireless transmitter and a wireless receiverthat transmits or receives signals using, for example, radio, WiFi andBluetooth, arranged on the stationary structure and the rotatingstructure respectively.

According to a preferred implementation of the multi-line Lidar of thepresent disclosure, the emission module includes multiple laser devicesfixedly arranged in the rotating structure, to realize the nonuniformvertical angular resolutions of the emitted multiple laser beams. Themultiple laser devices are grouped into multiple groups. Each group oflaser devices are spaced equally in the vertical direction, and gapsbetween adjacent laser devices in different groups may be same ordifferent, as long as the emitted multiple laser beams have a verticalangular resolution focusing on a key region.

In an embodiment, the key region indicates a middle region in a verticalfield of view angle range of the emission module. That is, compared withan upper region and a lower region of the vertical field of view anglerange of the emission module, more laser devices emit laser beams to themiddle region of the vertical field of view angle range.

According to a preferred implementation of the multi-line Lidar of thepresent disclosure, the laser devices are fixedly arranged on multiplesupporting structures in the rotating structure. The supportingstructures are arranged so that more laser devices emit laser beams tothe middle region of the vertical field of view angle range of theemission module, compared with the upper region and the lower region ofthe vertical field of view angle range. Similar, the laser devices maybe spaced equally or spaced unequally on the supporting structures. Gapsbetween adjacent laser devices in different supporting structures may besame or different.

According to a preferred implementation of the multi-line Lidar of thepresent disclosure, a first vertical plane in which the laser beamemitted by the emission module and a second vertical plane in which theecho signal is received by the receiving module are symmetric withrespect to a vertical plane that passes through a rotation center of therotating structure.

BRIEF DESCRIPTION OF THE DRAWINGS

The above attributes, features and advantages of the present disclosureand implementations thereof become clearer and easier to be understoodthrough the following illustrative description of embodiments, and areexplained in detail with reference to the accompanying drawingshereinafter.

FIG. 1 is a schematic structural diagram of a multi-line Lidar accordingto the present disclosure.

FIG. 2 schematically shows multiple laser devices of an emission modulefor emitting multiple laser beams for detecting fixedly arranged in arotating structure; in which, more laser devices emit laser beams to amiddle region compared with an upper region and a lower region.

FIG. 3 schematically shows that laser devices are arranged on multiplesupporting structures; in which, more laser beams are emitted into themiddle region by superposing of the number of supporting structures inthe middle region.

FIG. 4 schematically shows another example in which laser devices arearranged on multiple supporting structures, each supporting structuressupports multiple groups of laser devices, and more groups of laserdevices superpose in the middle region.

FIG. 5 schematically shows an embodiment of a multi-line Lidar accordingto the present disclosure, in which, an emission module for emittingmultiple laser beams for detecting, a dichroic module and a scanningmodule are arranged on a same axis.

FIG. 6 schematically shows the emission module and the receiving modulesymmetrically arranged with respect to a vertical plane passing througha rotation center of a rotating structure.

DETAILED DESCRIPTION OF EMBODIMENTS

FIG. 1 shows a multi-line Lidar 1 according to a first embodiment of thepresent disclosure. The multi-line Lidar 1 includes a stationarystructure 210, a rotating structure 240, and a rotation mechanism 250for driving the rotating structure 240 to rotate with respect to thestationary structure 210. A communication system and an electricalenergy transmission system are further provided between the stationarystructure 210 and the rotating structure 240.

A main body of the stationary structure 210 is a machined metal housing.A rotary axis penetrating the whole multi-line Lidar 1 in a verticaldirection is provided at a center of the stationary structure 210.Rotary components of the multi-line Lidar system (the rotating structure240, and communication/electrical energy transmission system between thestationary structure 210 and the rotating structure) each are installedon the rotary axis. In addition, the stationary structure is providedwith a circuit board. The circuit board is configured to convert a powersupply voltage in a wide range (such as, ranging from 7V to 32V)inputted from the outside into a voltage required for the multi-lineLidar system (such as 12V, 5V and 3.3V), convert an instruction and aGPS time synchronization signal sent from the outside into aninstruction and a GPS time synchronization signal with a formatacceptable by an internal circuit system of the multi-line Lidar, andconvert point cloud information obtained by scanning by the Lidar intoinformation with a format acceptable by the outside and output theinformation. An external data interface of the Lidar may be Ethernet,CAN bus, USB and so on.

A main body of the rotating structure 240 is also a machined metalhousing. The rotating structure 240 is installed on a rotary axis of thestationary structure through one or more bearings and is rotatablearound the rotary axis.

The stationary structure 210 is configured to fix the multi-line Lidar 1with an external connection structure. The external communicationinterface 220 provided in the stationary structure 210 is configured toreceive an external instruction, and transmit point cloud informationscanned by the multi-line Lidar 1 to the outside and so on. The externalpower supply interface 230 is configured to receive electrical energyinputted from the outside. The external electrical energy is inputtedfrom the external power supply interface 230 to the stationarystructure, and provided to the rotating structure 240 via an electricalenergy transmission system between the stationary structure 210 and therotating structure 240. The communication and electrical energytransmission between the stationary structure 210 and the rotatingstructure 240 is realized through the communication system and theelectrical energy transmission system between the stationary structure210 and the rotating structure 240. The communication system and theelectrical energy transmission system between the stationary structure210 and the rotating structure 240 are mainly configured to realizereliable data transmission and electrical energy transmission betweentwo movable connection structures. In the embodiment, communication andelectrical energy transmission are realized through a slip ring. Astator of the slip ring is connected to the stationary structure 210 ofthe Lidar, and a rotor of the slip ring is connected to the rotatingstructure 240 of the Lidar. During rotation, a signal is transmittedthrough a signal channel formed by the slip ring, and electrical energyis transmitted through a conductive channel formed by the slip ring.

Multiple emission modules 110 for emitting multiple laser beams fordetecting ranges and receiving modules 120 for receiving an echo signalare fixedly arranged on the rotating structure 240. The emission module110 emits multiple beams of lasers with different fixed angles in avertical direction. The receiving module 120 detects an echo signalgenerated by the backscattering of emitted laser beams by an obstacle.In the embodiment, the emission module 110 is implemented as multiplelaser devices 112, such as a semiconductor laser device with TO packageor chip packaging. Multiple laser devices 112 are arranged at differentpositions in a single circuit board. A control circuit 115 of each forthe laser devices 112 intermittently emits pulse current to drive thelaser device 112 to emit a laser pulse.

Light emitted from a single laser device 112 is collimated through anoptical system of the emission module 110, thereby forming approximatelyparallel beams. The laser devices 112 are located near a focal plane ofan optical system of the emission module. Therefore, light emitted bythe laser devices 112 having different positions in the verticaldirection forms beams with different angles in the vertical directionafter passing through the optical system of the emission module.

In the embodiment, the receiving module 120 is implemented as multiplephoton detectors, such as photodiodes, particularly avalanchephotodiodes. Multiple photon detectors are arranged at differentpositions in a signal circuit board.

The photon detector is arranged near the focal plane of the opticalsystem of the receiving module 120. Each photon detector is configuredto receive light in a direction the same as a direction of a beam oflaser emitted by the laser emission module. A receiving field of viewangle of each photon detector is determined based on a size of aphotosurface of the photon detector and a focal length of the opticalsystem of the receiving module. The receiving field of view angle of thephoton detector should be designed as small as possible, to reduceinterference from ambient light. An optical signal received by thephoton detector is converted into an electrical signal through asubsequent circuit, for calculating time of flight of the optical pulse.

The emission module 110 sends a signal to a correspondingtime-to-digital converter in emitting each line of ranging laser, andthe receiving module 120 sends a signal to the time-to-digital converterin response to detecting return laser. The ranging informationdetermination module 150 is coupled with the emission module 110 and thereceiving module 120 via an electrical signal. The ranging informationdetermination module obtains a time delay between a time instant whenthe laser is emitted and a time instant when the echo signal isreceived, by calculating a time delay of the two signals above, that is,time of flight of the laser, thereby calculating distances of theobstacles Z in predetermined directions. Here, the ranging informationdetermination module is arranged on the rotating structure. Afterobtaining the distance of the obstacles for each beam of laser in thevertical direction, the ranging information determination moduletransmits the ranging information to circuits on the stationarystructure separately or by packaging through the communication systembetween the stationary structure and the rotating structure. Athree-dimensional scenario around the Lidar can be established accordingto the ranging information. In other embodiments, the ranginginformation determination module may be arranged on the stationarystructure, or a part of the ranging information determination module isarranged on the rotating structure and another part of the ranginginformation determination module is arranged on the stationarystructure.

In the embodiment, the rotation mechanism 250 includes a direct currentbrushless motor with hollow shaft. A rotary axis passes through a hollowpart of the motor, a stator of the motor is fixed to the stationarystructure 210 of the multi-line Lidar 1 via threaded connection, and viaa coupler a rotor of the motor is connected to the rotating structure240 of the multi-line Lidar 1. The rotation of the motor drives therotor of the Lidar to rotate. In addition, the rotation mechanism 250includes a photoelectric encoder serving as a rotational angle feedbackdevice. A coded disc of the photoelectric encoder is installed on therotating structure 240 of the Lidar, and a photon detector of thephotoelectric encoder is installed on the stationary structure of theLidar and directly faces grids of the coded disc. When the motor drivesthe rotating structure 240 of the Lidar to rotate, a control circuit ofthe motor obtains information of the rotating structure 240 such as arotational angle and a rotation speed by reading a signal returned bythe photoelectric encoder, thereby obtaining angles of the measurementlasers in the horizontal direction.

The direct current brushless motor is driven by a special drive circuit.A rotation speed of the motor is controlled to be in a certain range bya closed-loop control system. The speed of the motor may be fed backfrom the photoelectric encoder or a back electromotive force and currentof the motor measured by the drive circuit of the motor. The close-loopcontrol algorithm may be implemented by a special motor drive chip (suchas TI DRV 10983), a single chip microcomputer or FPGA. The whole motorcontrol circuit may be implemented as a single circuit board. In a casethat the motor is installed in the stationary structure of the Lidar,the motor control circuit may be integrated on a circuit board in therotating structure.

A multi-line Lidar 1 is provided according to a second embodiment of thepresent disclosure. The second embodiment differs from the firstembodiment in that: the emission module 110 emits a single beam ormultiple beams of lasers having changed angles in the verticaldirection, and echo signals generated by the backscattering of emittedlaser beams by the obstacle Z are detected by the receiving module 120.In addition, the emission module 110 includes multiple circuit boardsprovided with laser devices 112, and the circuit boards are arranged atdifferent positions spatially. Similarly, the receiving module 120 alsoincludes multiple circuit boards provided with photon detectors, and thecircuit boards are arranged at different positions spatially.

The analog-to-digital converter of the ranging information determiningmodule collects a current waveform of laser emitted by the laseremission module and a current waveform of laser received by the laserreceiving module in real time, and digitizes, in real time, the currentwaveforms and inputs the digitized current waveforms into a single chipmicrocomputer or FPGA with a time calculating function. The single chipmicrocomputer or FPGA calculates a time delay between the emissionwaveform and the receiving waveform, and thus a flying distance of thelaser is obtained, thereby calculating a distance of the obstacles Z inthe direction.

In addition, in the embodiment, communication between the stationarystructure 210 and the rotating structure 240 is realized through opticaltransmission. The communication system between the stationary structure210 and the rotating structure 240 includes: a light emitting diodearranged on the stationary structure 210, a photodiode arranged on therotating structure, a light emitting diode arranged on the rotatingstructure 240 and a photodiode arranged on the stationary structure. Thelight emitting diode arranged on the stationary structure 210 convertsan electrical signal to be transmitted into an optical signal, and theoptical signal is captured and converted into an electrical signal bythe photodiode arranged on the rotating structure 240. The lightemitting diode arranged on the rotating structure 240 converts anelectrical signal to be transmitted into an optical signal, and theoptical signal is captured by the photodiode arranged on the rotatingstructure 210.

In addition, in the embodiment, electrical energy is transmitted betweenthe stationary structure 210 and the rotating structure 240 byelectromagnetic induction. The stationary structure of the multi-lineLidar 1 is provided with an emission coil, and the rotating structure ofthe multi-line Lidar 1 is provided with a receiving coil. Both theemission coil and the receiving coil are sleeved on the rotary axis ofthe Lidar. During the rotation of the rotating structure, a small gap ismaintained between the two coils all the time. The inputted electricalenergy is converted into alternating current via a modulation circuit,an alternating magnetic field is generated on the emission coil, andthus electromotive force is induced on the receiving coil. Thealternating current on the receiving coil is converted into directcurrent required by a circuit system of the rotating structure via themodulation circuit.

A multi-line Lidar 1 is provided according to a third embodiment of thepresent disclosure. The third embodiment differs from the aboveembodiments in that: the communication between the stationary structure210 and the rotating structure 240 is realized through a wirelesssending device and a wireless receiving device arranged on thestationary structure 210 and the rotating structure 240 respectively,instead of realizing through slip ring connection or a photoelectricmanner. Practically, the communication may be implemented by WiFi orBluetooth.

A multi-line Lidar 1 is provided according to a fourth embodiment of thepresent disclosure. In which, laser devices 112 or laser device unitarray is arranged appropriately, so that the generated laser beams aredistributed in a nonuniform mode in a vertical field of view range of−16°˜+7° (a nonuniform field of view from the up and the low). In which,a vertical angular resolution corresponding to a range of +2°˜+7° is 1°(corresponding to the first to sixth laser beam). A range of −6°˜+2° isan encryption subdivision segment, and has a vertical angular resolutionof ⅓° (corresponding to the sixth to the thirtieth laser beam). Avertical angular resolution corresponding to a range of −16°˜−6° is 1°(corresponding to the thirtieth to fortieth laser beam). Apparently, theabove resolutions can be realized by alternately arranging the laserdevices 112 or realized by multiple unit arrays consist of the laserdevices 112. Alternatively, in a variation of the embodiment, laserbeams with a nonuniform distribution can be realized by the laserdevices 112 or detectors spaced unequally in the same array.

Regarding the generation of multiple laser beams, a fifth embodimentaccording to the present disclosure differs from the fourth embodimentin that: multiple laser beams formed by a single beam of measurementlaser changing over time are disclosed. Here, the multiple laser beamsare not multiple beams of laser emitted from multiple laser devices 112simultaneously, but is a single beam of laser emitted by a single laserdevice 112 in combination with a galvanometer or a similar object, andan angle of the laser changes over time to perform multi-line scanning.According to the principle, the laser beam emitted from the laseremission module passes through the dichroic module 140, and then isreflected to a target object (or the obstacle Z) through aone-dimensional galvanometer or a two-dimensional galvanometer. Thelaser beam is reflected by the target object (or the obstacle Z), isincident to the dichroic module 140 via the galvanometer, and then istransmitted to a receiving focus element (such as a lens or a lensgroup). The laser is converged by the lens and then is incident to adetector module. The detector calculates time of flight of the laser byrecording a time delay between a time instant when the laser is emittedand a time instant when an echo signal is received, thereby obtainingdistance information of an object to be detected at this point. At anext time instant, the galvanometer reflects the laser to a next pointin space, and the detector obtains distance information on the point.The measurement process is repeated in cooperation with rotation of thelens, thereby completing scanning of the space by the single beam oflaser at a certain time period, and thus performing multi-line scanningon point cloud information in a whole detection range.

According to a variation of the fifth embodiment, for example, thegalvanometer is combined with multiple laser devices 112 arrangedfixedly, to generate multiple beams of laser having angles changing inthe vertical direction. For example, in order to realize the effect offorty lines, five laser devices 112 are adopted, and a single beam oflaser emitted from each laser device 112 is controlled to change anangle over time by a one-dimensional galvanometer or two-dimensionalgalvanometer to perform multi-line scanning, thereby completing scanningin a certain range. The five laser devices 112 together realize theeffect of forty lines scanning.

According to a sixth embodiment of the present disclosure, as shown inFIG. 5 , the emission module 110 (including a laser device 112 and acollimation module 114), the dichroic module 140 and the scanning module130 are arranged on a same axis, so that an emission optical path I anda receiving optical path R maintain a coaxial effect. The ranging lasertransmitting the dichroic module 140 is reflected to the obstacle Z inthe surrounding space by a galvanometer which can freely swing in ahorizontal and/or vertical space, and a reflection echo laser of theobstacle Z reflected by the scanning module is reflected to thereceiving module 120.

The laser device 112 of the emission module 110 may be a semiconductorlaser device, a fiber laser device and so on. Different types of laserdevices can emit laser pulses with different wavelengths. For example,the semiconductor laser device may generate and emit an infrared pulse.In specific implementation, in order to avoid interference betweendifferent Lidar systems, the emission module 110 may be controlled togenerate and emit laser pulses with a predetermined length.

The receiving module may include a converging module 116 and a detectingmodule 118. The detecting module 118 may be a photon detector. Theconverging module 116 and the collimation module 114 of the emissionmodule 110 may be lens.

The dichroic module 140 may be a perforated reflector, asemi-transparent mirror, a polarizing beam splitter and a coatedreflector and so on. The dichroic module 140 is configured to transmitparallel laser pulses adjusted by the collimation module 114, andreflect echo laser pulses reflected by the reflection scanning module17.

The scanning module 130 may be a one-dimensional or two-dimensionalgalvanometer, for example, an electrostatic galvanometer, a batterygalvanometer, a voltage galvanometer and an electric heatinggalvanometer.

According to a seventh embodiment of the present disclosure, in order tocause upper and lower regions S have a sparser vertical angularresolution than a middle region M in the vertical field of view anglerange, the multiple laser devices 112 are arranged nonuniformly in thevertical direction, that is, the density of the laser devices is firstincreased and then decreased from top to bottom, as shown in FIG. 2 . Inorder to realize the nonuniform distribution, the multiple laser devices112 fixedly arranged in the rotating structure may be grouped intomultiple groups according to different gaps between the laser devices.Denser laser beams are distributed in the key middle region in the aboveangle range.

According to a variation of the seventh embodiment, the rotatingstructure is provided with multiple supporting structures 119. The laserdevices 112 are arranged fixedly on the supporting structures 119respectively, so that laser beams emitted from more laser devices 112are distributed in the middle region M of the angle range of the laserbeam emitted from the emission module 110, compared with the upper andlower regions S of the angle range.

FIG. 3 schematically shows that the laser devices are arranged onmultiple supporting structures. Optical paths of the laser devices 112arranged on the supporting structures 119 are arranged alternately andsuperpose, so that more laser beams are emitted to the middle region bysuperposing of the number of the supporting structures 119.

FIG. 4 schematically shows another example in which the laser devicesare arranged on the supporting structures. FIG. 4 shows eight supportingstructures 119, five laser devices 112 are arranged on each supportingstructure 119, and the laser devices 112 are spaced equally. Five fixingplates are vertically arranged in an emission cavity and are separatedfrom each other in a horizontal direction. The supporting structures 119are fixed at a lateral portion of the fixing plate. The numbers ofsupporting structures fixed on different fixing plates are different,for example, the numbers of supporting structures 119 fixed on eachfixing plate, from left to right, are 2, 1, 2, 2 and 1 respectively.Projection points of the laser devices 112 in a vertical plane includinga main axis of the light collimation device have different densitydistribution in the up-down direction, for example, dense in the middleregion and sparse in the upper and lower regions, so that the multiplebeams of detection laser emitted from the laser devices 112 aredistributed densely at the horizontal line and regions close to thehorizontal line, and are distributed sparsely in other directions.

The preferred embodiments of the present disclosure are described above,but the disclosed embodiments are not intended to limit the spirit andscope of the present disclosure. Those skilled in the art can make moreembodiments and applications according to teaching of the presentdisclosure, and these embodiments and applications should not beregarded as departing from the spirit and scope of the presentdisclosure. The spirit and scope of the present disclosure are definedby the claims rather than the specific embodiments.

REFERENCE NUMERAL LIST

-   1 Multi-line Lidar-   110 Emission module for emitting multiple laser beams for detecting    ranges-   120 Receiving module for receiving an echo signal-   210 Stationary structure-   220 External communication interface-   230 External power supply interface-   240 Rotating structure-   250 Rotation mechanism-   130 Scanning module-   140 dichroic module-   112 Laser device-   114 Collimation module-   116 Converging module-   118 Detecting module-   119 Supporting structure-   I Emission optical path-   R Receiving optical path-   Z Obstacle-   S Upper and lower regions-   M Middle region

The invention claimed is:
 1. A multi-line Lidar, comprising: a rotatingstructure comprising an emission module and a receiving module; theemission module comprising a plurality of laser devices and configuredto emit a plurality of laser beams for detecting ranges, wherein theplurality of laser devices are disposed on at least one supportingstructure having an axis in a vertical direction, wherein a distributiondensity of laser devices at a middle region of the at least onesupporting structure along the vertical direction is greater than adistribution density of laser devices at an upper region and a lowerregion of the at least one supporting structure along the verticaldirection; the receiving module comprising one or more photon detectorsand configured to detect an echo signal generated by backscattering ofthe plurality of laser beams by one or more obstacles; a ranginginformation determination module coupled with the emission module andthe receiving module via electrical signals, and configured to determineone or more distances of the one or more obstacles in predetermineddirections based on a time delay between a first time instant when theemission module emits the plurality of laser beams and a second timeinstant when the echo signal is received by the receiving module; and acontrol circuit and an optical system for the emission module and thereceiving module.
 2. The multi-line Lidar according to claim 1, whereinthe emission module is configured to emit the plurality of laser beamswith nonuniform vertical angular resolutions.
 3. The multi-line Lidaraccording to claim 1, wherein the control circuit comprises atime-to-digital converter, and the ranging information determinationmodule is configured to determine the time delay based on a first signalsent by the emission module to the time-to-digital converter and asecond signal sent by the receiving module to the time-to-digitalconverter.
 4. The multi-line Lidar according to claim 1, wherein thecontrol circuit comprises an analog-to-digital converter configured tocollect and digitize, in real time, current waveforms of the emissionmodule and the receiving module; and the ranging informationdetermination module is configured to compare the current waveform ofthe emission module and the current waveform of the receiving module fordetermining the time delay.
 5. The multi-line Lidar according to claim1, wherein the emission module is configured to transmit the pluralityof laser beams in a manner that laser beams in the upper region and thelower region have a sparser vertical angular resolution along a verticalfield of view than laser beams in the middle region.
 6. The multi-lineLidar according to claim 1, further comprising: a scanning moduleconfigured to change an angle of the plurality of laser beams over timein the vertical direction.
 7. The multi-line Lidar according to claim 6,further comprising: a dichroic module disposed on a same axis with theemission module and the scanning module, wherein the dichroic module isconfigured to transmit a laser beam emitted from the emission module tothe scanning module and reflect an echo signal of the laser beam to thereceiving module.
 8. The multi-line Lidar according to claim 1, furthercomprising: a stationary structure, wherein the stationary structure hasan external communication interface and an external power supplyinterface, and an electrical energy transmission system suppliesexternal electrical energy to the rotating structure via the externalpower supply interface; a rotation mechanism configured to drive therotating structure to rotate with respect to the stationary structure,wherein the rotation mechanism comprises a feedback device configured todetect a rotational angle of the rotation mechanism in a horizontaldirection; a communication system for transmitting signals between therotating structure and the stationary structure; and the electricalenergy transmission system for transmitting electrical energy betweenthe rotating structure and the stationary structure.
 9. The multi-lineLidar according to claim 8, wherein the stationary structure is providedwith an emission coil and a first modulation circuit, the rotatingstructure is provided with a receiving coil and a second modulationcircuit, and the emission coil and the receiving coil are configured totransmit electrical energy from the emission coil to the receiving coilby electromagnetic induction.
 10. The multi-line Lidar according toclaim 8, wherein the stationary structure is connected to the rotatingstructure via a slip ring having two portions that form a conductivechannel, and the conductive channel is configured to transmit electricalenergy between the stationary structure and the rotating structure. 11.The multi-line Lidar according to claim 10, wherein the two portions ofthe slip ring further form a signal channel.
 12. The multi-line Lidaraccording to claim 8, wherein the communication system arranged betweenthe stationary structure and the rotating structure comprises a firstlight emitting diode and a first photodiode disposed on the stationarystructure and a second light emitting diode and a second photodiodedisposed on the rotating structure.
 13. The multi-line Lidar accordingto claim 8, wherein the communication system between the stationarystructure and rotating structure comprises a wireless transmitter and awireless receiver arranged on the stationary structure and the rotatingstructure respectively, and the wireless transmitter transmits signalsand the wireless receiver receives signals using radio, WiFi, orBluetooth.
 14. The multi-line Lidar according to claim 8, wherein theemission module further comprises a second plurality of laser devices.15. The multi-line Lidar according to claim 14, wherein the secondplurality of laser devices are attached to a second supportingstructure.
 16. The multi-line Lidar according to claim 8, wherein afirst vertical plane of the emission module and a second vertical planeof the receiving module are symmetrical with respect to a vertical planethat passes through a rotation center of the rotating structure.
 17. Themulti-line Lidar according to claim 1, wherein one or more beams of theplurality of laser beams emitted by the emission module have an anglechanging over time in the vertical direction.